In the conventional projection device, an illumination light beam provided by a light source is usually homogenized by a light integration rod, and then the illumination light beam is reflected by a reflective mirror to a light valve, and a light spot is formed on the light valve. In general, in order to have preferred light utilization efficiency, it is generally desirable to have the light spot just entirely cover an active area of the light valve and focus on the active area. However, due to different reflection optical paths, tolerances of the finished molds, or tolerances during assembling, the light spot formed on the light valve sometimes fails to focus on the active area, and the edge of the light spot diverges, resulting in poor light utilization efficiency.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already conventional to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.